<?php
# Smart Image Resizer 1.4.1
# Resizes images, intelligently sharpens, crops based on width:height ratios, color fills
# transparent GIFs and PNGs, and caches variations for optimal performance

# Created by: Joe Lencioni (http://shiftingpixel.com)
# Date: August 6, 2008
# Based on: http://veryraw.com/history/2005/03/image-resizing-with-php/

/////////////////////
// REQUIREMENTS
/////////////////////

# PHP and GD

/////////////////////
// PARAMETERS
/////////////////////

# Parameters need to be passed in through the URL's query string:
# image		absolute path of local image starting with "/" (e.g. /images/toast.jpg)
# width		maximum width of final image in pixels (e.g. 700)
# height		maximum height of final image in pixels (e.g. 700)
# color		(optional) background hex color for filling transparent PNGs (e.g. 900 or 16a942)
# cropratio	(optional) ratio of width to height to crop final image (e.g. 1:1 or 3:2)
# nocache		(optional) does not read image from the cache
# quality		(optional, 0-100, default: 90) quality of output image

/////////////////////
// EXAMPLES
/////////////////////

# Resizing a JPEG:
# <img src="image.php?width=100&amp;height=100&amp;image=/path/to/image.jpg" />

# Resizing and cropping a JPEG into a square:
# <img src="image.php?width=100&amp;height=100&amp;cropratio=1:1&amp;image=/path/to/image.jpg" />

# Matting a PNG with #990000:
# <img src="image.php?color=900&amp;image=/path/to/image.png" />

/////////////////////
// CODE STARTS HERE
/////////////////////

if (!isset($_GET['image'])) {
	header('HTTP/1.1 400 Bad Request');
	echo 'Error: no image was specified';
	exit();
}

define('MEMORY_TO_ALLOCATE',	'100M');
define('DEFAULT_QUALITY',		90);
define('CURRENT_DIR',			dirname(__FILE__));
define('CACHE_DIR_NAME',		'/imagecache/');
define('CACHE_DIR',				CURRENT_DIR . CACHE_DIR_NAME);
define('DOCUMENT_ROOT',			$_SERVER['DOCUMENT_ROOT']);

# Images must be local files, so for convenience we strip the domain if it's there
$image			= preg_replace('/^(s?f|ht)tps?:\/\/[^\/]+/i', '', (string) $_GET['image']);

# For security, directories cannot contain ':', images cannot contain '..' or '<', and  images must start with '/'
if ($image{0} != '/' || strpos(dirname($image), ':') || preg_match('/(\.\.|<|>)/', $image)) {
	header('HTTP/1.1 400 Bad Request');
	echo 'Error: malformed image path. Image paths must begin with \'/\'';
	exit();
}

# If the image doesn't exist, or we haven't been told what it is, there's nothing that we can do
if (!$image) {
	header('HTTP/1.1 400 Bad Request');
	echo 'Error: no image was specified';
	exit();
}

# Strip the possible trailing slash off the document root
$docRoot	= preg_replace('/\/$/', '', DOCUMENT_ROOT);
//echo $docRoot . $image;exit;
if (!file_exists($docRoot . $image)) {
	header('HTTP/1.1 404 Not Found');
	echo 'Error: image does not exist: ' . $docRoot . $image;
	exit();
}

# Get the size and MIME type of the requested image
$size	= GetImageSize($docRoot . $image);
$mime	= $size['mime'];

# Make sure that the requested file is actually an image
if (substr($mime, 0, 6) != 'image/') {
	header('HTTP/1.1 400 Bad Request');
	echo 'Error: requested file is not an accepted type: ' . $docRoot . $image;
	exit();
}

$width			= $size[0];
$height			= $size[1];

$maxWidth		= (isset($_GET['width'])) ? (int) $_GET['width'] : 0;
$maxHeight		= (isset($_GET['height'])) ? (int) $_GET['height'] : 0;

if (isset($_GET['color']))
	$color		= preg_replace('/[^0-9a-fA-F]/', '', (string) $_GET['color']);
else
	$color		= FALSE;

# If either a max width or max height are not specified, we default to something large so the unspecified dimension isn't a constraint on our resized image.
# If neither are specified but the color is, we aren't going to be resizing at all, just coloring.
if (!$maxWidth && $maxHeight) {
	$maxWidth	= 99999999999999;
} elseif ($maxWidth && !$maxHeight) {
	$maxHeight	= 99999999999999;
} elseif ($color && !$maxWidth && !$maxHeight) {
	$maxWidth	= $width;
	$maxHeight	= $height;
}

# If we don't have a max width or max height, OR the image is smaller than both we do not want to resize it, so we simply output the original image and exit
if ((!$maxWidth && !$maxHeight) || (!$color && $maxWidth >= $width && $maxHeight >= $height)) {
	$data	= file_get_contents($docRoot . '/' . $image);
	
	$lastModifiedString	= gmdate('D, d M Y H:i:s', filemtime($docRoot . '/' . $image)) . ' GMT';
	$etag				= md5($data);
	
	doConditionalGet($etag, $lastModifiedString);
	
	header("Content-type: $mime");
	header('Content-Length: ' . strlen($data));
	echo $data;
	exit();
}

# Ratio cropping
$offsetX	= 0;
$offsetY	= 0;

if (isset($_GET['cropratio'])) {
	$cropRatio		= explode(':', (string) $_GET['cropratio']);
	if (count($cropRatio) == 2)	{
		$ratioComputed		= $width / $height;
		$cropRatioComputed	= (float) $cropRatio[0] / (float) $cropRatio[1];
		
		if ($ratioComputed < $cropRatioComputed) { # Image is too tall so we will crop the top and bottom
			$origHeight	= $height;
			$height		= $width / $cropRatioComputed;
			$offsetY	= ($origHeight - $height) / 2;
		} else if ($ratioComputed > $cropRatioComputed) { # Image is too wide so we will crop off the left and right sides
			$origWidth	= $width;
			$width		= $height * $cropRatioComputed;
			$offsetX	= ($origWidth - $width) / 2;
		}
	}
}

# Setting up the ratios needed for resizing. We will compare these below to determine how to resize the image (based on height or based on width)
$xRatio		= $maxWidth / $width;
$yRatio		= $maxHeight / $height;

if ($xRatio * $height < $maxHeight){ # Resize the image based on width
	$tnHeight	= ceil($xRatio * $height);
	$tnWidth	= $maxWidth;
}else { # Resize the image based on height
	$tnWidth	= ceil($yRatio * $width);
 	$tnHeight	= $maxHeight;
}

# Determine the quality of the output image
$quality	= (isset($_GET['quality'])) ? (int) $_GET['quality'] : DEFAULT_QUALITY;

# Before we actually do any crazy resizing of the image, we want to make sure that we haven't already done this one at these dimensions. To the cache!
# Note, cache must be world-readable. We store our cached image filenames as a hash of the dimensions and the original filename

$resizedImageSource		= $tnWidth . 'x' . $tnHeight . 'x' . $quality;
if ($color)
	$resizedImageSource	.= 'x' . $color;
if (isset($_GET['cropratio']))
	$resizedImageSource	.= 'x' . (string) $_GET['cropratio'];
$resizedImageSource		.= '-' . $image;

$resizedImage	= md5($resizedImageSource);
	
$resized		= CACHE_DIR . $resizedImage;

# Check the modified times of the cached file and the original file. If the original file is older than the cached file, then we simply serve up the cached file
if (!isset($_GET['nocache']) && file_exists($resized)) {
	$imageModified	= filemtime($docRoot . $image);
	$thumbModified	= filemtime($resized);
	
	if($imageModified < $thumbModified) {
		$data	= file_get_contents($resized);
	
		$lastModifiedString	= gmdate('D, d M Y H:i:s', $thumbModified) . ' GMT';
		$etag				= md5($data);
		
		doConditionalGet($etag, $lastModifiedString);
		
		header("Content-type: $mime");
		header('Content-Length: ' . strlen($data));
		echo $data;
		exit();
	}
}

# We don't want to run out of memory
ini_set('memory_limit', MEMORY_TO_ALLOCATE);

# Set up a blank canvas for our resized image (destination)
$dst	= imagecreatetruecolor($tnWidth, $tnHeight);

# Set up the appropriate image handling functions based on the original image's mime type
switch ($size['mime'])
{
	case 'image/gif':
		# We will be converting GIFs to PNGs to avoid transparency issues when resizing GIFs. This is maybe not the ideal solution, but IE6 can suck it
		$creationFunction	= 'ImageCreateFromGif';
		$outputFunction		= 'ImagePng';
		$mime				= 'image/png'; # We need to convert GIFs to PNGs
		$doSharpen			= FALSE;
		$quality			= round(10 - ($quality / 10)); # We are converting the GIF to a PNG and PNG needs a compression level of 0 (no compression) through 9
	break;
	
	case 'image/x-png':
	case 'image/png':
		$creationFunction	= 'ImageCreateFromPng';
		$outputFunction		= 'ImagePng';
		$doSharpen			= FALSE;
		$quality			= round(10 - ($quality / 10)); # PNG needs a compression level of 0 (no compression) through 9
	break;
	
	default:
		$creationFunction	= 'ImageCreateFromJpeg';
		$outputFunction	 	= 'ImageJpeg';
		$doSharpen			= TRUE;
	break;
}

# Read in the original image
$src	= $creationFunction($docRoot . $image);

if (in_array($size['mime'], array('image/gif', 'image/png'))) {
	if (!$color) {
		# If this is a GIF or a PNG, we need to set up transparency
		imagealphablending($dst, false);
		imagesavealpha($dst, true);
	} else {
		# Fill the background with the specified color for matting purposes
		if ($color[0] == '#')
			$color = substr($color, 1);
		
		$background	= FALSE;
		
		if (strlen($color) == 6)
			$background	= imagecolorallocate($dst, hexdec($color[0].$color[1]), hexdec($color[2].$color[3]), hexdec($color[4].$color[5]));
		else if (strlen($color) == 3)
			$background	= imagecolorallocate($dst, hexdec($color[0].$color[0]), hexdec($color[1].$color[1]), hexdec($color[2].$color[2]));
		if ($background)
			imagefill($dst, 0, 0, $background);
	}
}

# Resample the original image into the resized canvas we set up earlier
ImageCopyResampled($dst, $src, 0, 0, $offsetX, $offsetY, $tnWidth, $tnHeight, $width, $height);

if ($doSharpen) {
	# Sharpen the image based on two things:
	#	(1) the difference between the original size and the final size
	#	(2) the final size
	$sharpness	= findSharp($width, $tnWidth);
	
	$sharpenMatrix	= array(
		array(-1, -2, -1),
		array(-2, $sharpness + 12, -2),
		array(-1, -2, -1)
	);
	$divisor		= $sharpness;
	$offset			= 0;
	imageconvolution($dst, $sharpenMatrix, $divisor, $offset);
}

# Make sure the cache exists. If it doesn't, then create it
if (!file_exists(CACHE_DIR))
	mkdir(CACHE_DIR, 0755);

# Make sure we can read and write the cache directory
if (!is_readable(CACHE_DIR)) {
	header('HTTP/1.1 500 Internal Server Error');
	echo 'Error: the cache directory is not readable';
	exit();
} else if (!is_writable(CACHE_DIR)) {
	header('HTTP/1.1 500 Internal Server Error');
	echo 'Error: the cache directory is not writable';
	exit();
}

# Write the resized image to the cache
$outputFunction($dst, $resized, $quality);

# Put the data of the resized image into a variable
ob_start();
$outputFunction($dst, null, $quality);
$data	= ob_get_contents();
ob_end_clean();

# Clean up the memory
ImageDestroy($src);
ImageDestroy($dst);

# See if the browser already has the image
$lastModifiedString	= gmdate('D, d M Y H:i:s', filemtime($resized)) . ' GMT';
$etag				= md5($data);

doConditionalGet($etag, $lastModifiedString);

# Send the image to the browser with some delicious headers
header("Content-type: $mime");
header('Content-Length: ' . strlen($data));
echo $data;

function findSharp($orig, $final) # function from Ryan Rud (http://adryrun.com)
{
	$final	= $final * (750.0 / $orig);
	$a		= 52;
	$b		= -0.27810650887573124;
	$c		= .00047337278106508946;
	
	$result = $a + $b * $final + $c * $final * $final;
	
	return max(round($result), 0);
} # findSharp()

function doConditionalGet($etag, $lastModified)
{
	header("Last-Modified: $lastModified");
	header("ETag: \"{$etag}\"");
		
	$if_none_match = isset($_SERVER['HTTP_IF_NONE_MATCH']) ?
		stripslashes($_SERVER['HTTP_IF_NONE_MATCH']) : 
		false;
	
	$if_modified_since = isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) ?
		stripslashes($_SERVER['HTTP_IF_MODIFIED_SINCE']) :
		false;
	
	if (!$if_modified_since && !$if_none_match)
		return;
	
	if ($if_none_match && $if_none_match != $etag && $if_none_match != '"' . $etag . '"')
		return; # etag is there but doesn't match
	
	if ($if_modified_since && $if_modified_since != $lastModified)
		return; # if-modified-since is there but doesn't match
	
	# Nothing has changed since their last request - serve a 304 and exit
	header('HTTP/1.1 304 Not Modified');
	exit();
} # doConditionalGet()
?>